Belize is located on the Caribbean coast of northern Central America. It shares a border on the north with the Mexican state of Quintana Roo, on the west with the Guatemalan department of Petén, and on the south with the Guatemalan department of Izabal. To the east in the Caribbean Sea, the second-longest barrier reef in the world flanks much of the 386 kilometers of predominantly marshy coastline. Small cay islands totaling about 690 square kilometers, dot the reef. The area of the country totals 22,960 square kilometers, an area slightly larger than El Salvador or Massachusetts. The abundance of lagoons along the coasts and in the northern interior reduces the actual land area to 21,400 square kilometers.

Belize is shaped like a rectangle that extends about 280 kilometers north-south and about 100 kilometers east-west, with a total land boundary length of 516 kilometers. The undulating courses of two rivers, the Hondo and the Sarstoon, define much of the course of the country's northern and southern boundaries. The western border follows no natural features and runs north-south through lowland forest and highland plateau.